2004 civic ex 73000 miles check engine light came on. had codes checked out at autozone. po134, po171, p2a00. Ox sensor circuit bank 1 lean blah blah blah. I replaced upstream o2 sensor and light went off. drove car 10 miles to get gas and light came on again. reset by disconnecting battery and turning ignition key to on. drove car 30 miles and light came on again. what should I be looking for now??? gas mileage is less than expected.

 

Next thing to do would be pull codes again. Whenever there is more than one code you want to see which ones may be old, and which ones will reoccur. P0171 and P0134 are probably both due to a general lean condition-- maybe low fuel pressure, clogged fuel injector, problem with MAF sensor, or leak in the exhaust manifold fooling the sensor.

Is the car modified in any way, or is it stock? Also does it generally run OK, except for CEL on and low gas mileage?

 

the car is bone stock and runs just fine. only problem is the bad fuel mileage which started just before the check engine light appeared

 

pulled codes again today P0171, and P2A00. also listed these same codes as pending. Autozone seemed to think the pending codes would be dropped soon if I would keep driving the car. what do you think???

 

replaced map sensor had the check engine light reset and after about 4-5 key cycles the light is back on with single code PO171. dont seem to have any vac leaks or noticable exaust leaks. gas mileage still sucks. what should i be looking for??? fuel pressure problem???